/Engine/Source/Editor/MovieSceneTools/Public/TrackEditors/SubTrackEditor.h
The purpose of this method is to disallow circular references between sub-sequences in the focused movie scene.
true if the sequence can be added as a sub-sequence, false otherwise.
bool CanAddSubSequence ( const [UMovieSceneSequence](API\Runtime\MovieScene\UMovieSceneSequence) & Sequence ) const